# Source : https://devcentral.f5.com/community/group/aft/1174729/asg/50
# Thanks to Forum User 'MaHHF5'

when CLIENT_ACCEPTED { 
  log local0. "ACC - got new connect" 
  set retries 0 
  set server_needed 0 
  set server_selected "none" 
} 

when HTTP_REQUEST { 
  # when opening Notes database, set server_needed 1 
  if {([HTTP::uri] ends_with ".nsf?OpenDatabase") and not ([HTTP::uri] contains "names.nsf") and not ([HTTP::uri] contains "iwaredir.nsf") and not ($server_selected == "new") and not ($server_selected == "orig") }{ 
    set original_request [HTTP::request] 
    set server_needed 1 
    set nsf "[substr [HTTP::uri] 1 ".nsf"].nsf" 
    log local0. "REQ - Server needed: $server_needed" 
    log local0. "REQ - NSF: $nsf" 
    HTTP::uri /iwaredir.nsf/ServersLookup?OpenForm&nsfpath=$nsf 
    log local0. "REQ - uri: /iwaredir.nsf/ServersLookup?OpenForm&nsfpath=$nsf" 
  } else { 
    set server_needed 0 
        set original_request [HTTP::request] 
  } 
  # when HTTP::retry with new server from X-header, select it from pool 
  if { $server_selected == "new" } { 
    pool [LB::server pool] member $dest 
    log local0. "REQ - Using selected new server [LB::server addr] of pool: [LB::server pool] (Destination: $dest)" 
  } 
} 

when LB_SELECTED { 
   # when HTTP::retry because of 404-Code, reselect member 
   # F5 unit sends a new session cookie 
   if { ($retries > 0) and ($retries < 9) } { 
    LB::reselect pool [LB::server pool] 
    log local0. "SELE - Reselection No. $retries" 
         } 
} 

when HTTP_RESPONSE { 
  log local0. "RESP - Used server [LB::server addr] of pool: [LB::server pool]" 

  # when 404-Code after automatic reselection of F5 unit to wrong server occurs, do another try 
  if { ([HTTP::status] == 404) and ($retries < 8) } { 
            log local0. "ALERT: 404" 
        incr retries 
                log local0. "RESP - Retrying original request with reselection No. $retries" 
                HTTP::retry $original_request 
        } 

  # generate new session cookie (code from DevCentral) after member selection based on X-Headers because the F5 unit does not send one 
  if { $server_selected == "new" } { 
    set member "[LB::server addr]" 
    scan $member "%u.%u.%u.%u" a b c d
    set pcookie "[scan [expr ($d<<24)|($c<<16)|($b<<8)|$a] %u].[expr 256*80].0000" 
    HTTP::cookie insert name BIGipServer[LB::server pool] value $pcookie path "/" 
    log local0. "RESP - New persistence cookie sent for $dest" 
        set server_selected "none" 
        } 
  # build list of iNotes-Server from X-Domino Header 
  if { $server_needed == 1} { 
	set server_list [split [HTTP::header X-Domino-ClusterServers], ,] 
    # set server_list2 [split [HTTP::header X-Domino-ReplicaServers], ,] 
    # set server_list "${server_list1} ${server_list2}" 
    # log local0. "RESP - Server_list_Cluster: $server_list1" 
    # log local0. "RESP - Server_list_Replica: $server_list2" 
    log local0. "RESP - Server_list: $server_list" 
    HTTP::collect [HTTP::header Content-Length] 

    # check if we are already on right server and then set server_selected "orig" 
    foreach {svr} $server_list { 
      if { "" ne $svr }{ 
        set dest [class search -value NSLOOKUPSERVER equals "[string trim $svr]"] 
                if {[LB::server addr] == $dest } { 
                        log local0. "RESP - Already on right server: $dest" 
            set server_selected "orig" 
                } 
      } 
    } 

    foreach {svr} $server_list { 
      if { "" ne $svr }{ 
#        set dest [class search -value NSLOOKUPSERVER equals "[string trim $svr]"] 
        # when on right server, do HTTP::retry 
                if { $server_selected == "orig" } { 
        log local0. "RESP - Retrying original request for original server" 
        HTTP::retry $original_request 
        break 
                } 
          # when server in list is up, do HTTP::retry 
        if { [LB::status pool [LB::server pool] member $dest 80] eq "up" } { 
        log local0. "RESP - Status of selected server $dest, pool [LB::server pool]: [LB::status pool [LB::server pool] member $dest 80]" 
        set server_selected "new" 
        log local0. "RESP - Retrying original request for new server" 
        HTTP::retry $original_request 
        break 
        } 
      } 
    } 

  } 
}